Seeing as she's been sober for 7+ years now, I highly doubt any of the material we have from her was written under the influence of anything other than her memories. Maybe weed, but I get the impression she really stays away from anything these days. Besides she already said that when she writes, she sits down and thinks of the way things used to be. I'd imagine most drugs would make writing (not to mention thinking) accurately and to a satisfying degree counter-productive.
you don't need to have taken drugs to write about them